Arnold was one of several co-directors for the fieldwork stages of the Fraser River Valley Archaeological Project in British Columbia, Canada, which started in 2002. Field work was largely concluded in 2006, and analyses and publication projects are now ongoing. Working with colleagues from Simon Fraser University (SFU), University of British Columbia, and the Sto:lo Nation (Coast Salish), UCLA team members focused on early village sites and late precontact and early colonial-era households in the Sto:lo region and their social and exchange relationships with other groups situated along the massive Fraser River system. The Fraser extends from deep in the Canadian Plateau to the Gulf of Georgia near Vancouver, and was one of the world's great rivers for salmon harvests.

Two of Arnold’s former PhD students conducted research in and around these areas: Anthony Graesch (PhD 2006) tested an early colonial village site on Greenwood Island near Hope for his doctoral project, and Michael Lenert (PhD 2007) coordinated with SFU on testing the 2,000-3,000 -year-old Katz site along the upper Fraser River for his dissertation fieldwork.
Sto:lo people have strongly embraced this project and participated extensively during all field seasons by hosting feasts, taking project members to inaccessible sites along the river, providing regional cultural landscape tours that recounted generations of oral narratives, and joining in the field testing of houses. The research team has focused on particular sites/communities in order to maximize the benefits from this project for promoting Sto:lo cultural heritage. Sto:lo cultural leader Sonny McHalsie and Sto:lo archaeologist Dave Schaepe spoke at UCLA's public lecture series in 2006.